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<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <script>
        //  手写Promise类
        class MyPromise {
            constructor(handle) {
                this['[[PromiseState]]'] = "pending";
                this['[[PromiseResult]]'] = undefined;
                handle(this._resolve.bind(this), this._reject.bind(this));
            }

            _resolve(val) {
                this['[[PromiseState]]'] = "fulfilled";
                this['[[PromiseResult]]'] = val;
            }
            _reject(err) {
                this['[[PromiseState]]'] = "rejected";
                this['[[PromiseResult]]'] = err;
            }
        }

        let p = new MyPromise((resolve, reject) => {
            reject("error");
        });
        console.log(p);
    </script>
</body>

</html>